Acetabular Prosthesis Inner Wall Geometry for Dislocation Resistance
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Solution Overview
Problem
Current acetabular orthopaedic prostheses face challenges in securely positioning and stabilizing the femoral head component, leading to potential dislocation due to inadequate design features that resist dislocation and provide sufficient range of motion in hip arthroplasty procedures.
Innovation Solution
The acetabular prosthesis features a cavity with an inner wall comprising a cylindrical surface and a semi-spherical surface, where the cylindrical surface extends to a greater depth on the inferior side than the superior side, and the semi-spherical surface extends through an imaginary plane, creating a cupped region that resists dislocation, along with a non-orthogonal angle between the central axes of the cylindrical and semi-spherical surfaces, enhancing stability and range of motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the inner wall of the acetabular prosthesis is designed with a cylindrical surface extending to greater depth on the inferior side, then dislocation resistance is improved, but the complexity of the prosthesis structure increases
Solution Approach 1:
The inner wall incorporates a semi-spherical surface that transitions from the cylindrical surface, creating a cupped region. This curved geometry naturally guides the femoral head into the correct position and provides progressive resistance to dislocation forces while maintaining structural integrity. The curvature distributes mechanical stresses more effectively than sharp angles or flat surfaces.
Solution Approach 2:
The cylindrical surface extends to a greater depth on the inferior side compared to the superior side, creating an asymmetric geometry. This asymmetry is deliberately designed to match the natural anatomy of the acetabulum and to provide directional resistance to dislocation forces. The non-orthogonal angle between the cylindrical and semi-spherical surfaces further emphasizes this asymmetric design, optimizing stability while managing structural complexity.
2Stability of the object's composition
If the semi-spherical surface extends through the imaginary plane to create a cupped region, then stability is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The semi-spherical surface provides a smooth, continuous curvature that is well-suited for conventional manufacturing processes. The transition from cylindrical to semi-spherical geometry is designed to be manufacturable while still achieving the desired stability. The cupped region created by this curvature provides natural guidance and constraint on the femoral head without requiring overly complex manufacturing precision.
3Adaptability or versatility
If the cavity is sized to position the geometric center of the femoral component lateral of the outer rim, then range of motion is improved, but the risk of dislocation increases
Solution Approach 1:
The inner wall geometry is designed in advance to preemptively guide the femoral head into the correct position and orientation. The cylindrical and semi-spherical surfaces work together to pre-constrain the femoral head, creating natural mechanical guides that prevent dislocation before it can occur. This preliminary geometric constraint allows for increased range of motion while maintaining safety.
Solution Approach 2:
The semi-spherical surface provides a natural articulation that matches the spherical geometry of the femoral head. This curvature allows for smooth, controlled movement through a greater range of motion while the cupped region created by extending through the imaginary plane provides progressive mechanical constraint that prevents dislocation. The geometry creates a natural mechanical stop that guides the femoral head back to its correct position.
Data Source
AI summary
An orthopaedic components, prostheses, and methods for a hip arthroplasty are disclosed. An acetabular prosthetic component includes an outer rim and a cavity defined by an inner wall. The cavity is sized to receive a femoral head of a femoral prosthetic component. The inner wall includes a curved surface extending inwardly from the outer rim to an inner end, and a semi-spherical surface connected to the inner end of the curved surface. The inner wall is shaped to resist dislocation of the femoral head component from the cavity and permit the femoral head component to articulate over a range of motion.